Illustration: Comparison of Piston Hydrogen Engine and Rotary Hydrogen Engine

Notice how the Piston mixture immediately comes into contact with the hot exhaust valve, causing pre-ignition (left). The Rotary mixture has the opportunity to burn cleanly before being exposed to the exhaust port (right).

AIr and hydrogen are admitted to the Rotary engine in a two-stage process. First, air is drawn into the combustion chamber through an intake port, which is then sealed off by the turning rotor. Next, hydrogen is injected during the compression cycle by a low-pressure pump. Injection timing is regulated by a small poppet valve in the injector. Water vapour is the principal consituent of hydrogen-combustion, so a catalytic converter isn't needed.